MARINATING: Break tamarind apart, place in a small saucepan with water. Simmer, covered, for about 10 minutes or until pasty coating separates from seeds. Press through a sieve or food mill to extract all pulp and soupy liquid. Discard seeds. Rinse shrimps thoroughly, pat dry and marinate fro 1 hour with 1 tablespoon of this tamarind liquid, the oyster sauce and hot chili sauce. COOKING: Meanwhile, cut young ginger into toothpick-sized slivers. If using mature ginger, peel and sliver. Peel and sliver garlic. Place blachan in a non-stick pan and heat gently fro 3 to 4 minutes to develop the flavors. Pell and cut red onions into wedges. Combine oyster, soy and chili sauces with blachan; stir into remaining tamarind liquid. Heat a large wok over high heat. When a drop of water sizzles immediately into steam pour in 2 tablespoons of the oil. Swirl up sides of wok, and when just at smoking point, dump in ginger and garlic. Stir fry until golden, about 3 to 4 minutes. Adding more oil as needed, stir frey shrimp in batches until orange red, about 3 minutes. Pour sauces over all the shrimp in the wok and cook at a brisk bubble over high heat until shrimps are aromatic and sauces have reduced and thickened to enrobe the shells, about 8 minutes. Mix in sugar and onion wedges, taste to adjust seasoning, sweetening and spiciness. Makes plenty for 6 as a principal dish with rice, enough for 8 with other dishes.